This invention relates to apparatus and method for making propellers. More specifically, this invention relates to an apparatus and method for quickly and easily making boat propellers from a hub and a plurality of blade blanks wherein the propeller has a selected blade pitch angle.
In the prior art, a wide variety of propeller designs are available for marine uses. That is, propellers are made having different overall diameters, different numbers of propeller blades, different blade pitch angles, different blade shapes or curvatures, and different blade sweep back angles. These design differences result from an attempt to match propeller operating characteristics to the particular propulsion needs of a given boat. Thus, the ideal design of a propeller depends upon the hull shape, size, and weight of the boat together with the desired average operating conditions of that boat. For example, in some boats such as radio controlled model racing boats, the propeller and the boat must be accurately matched with each other in order to achieve optimum speed and control.
Throughout the prior art, propellers large and small have traditionally been formed from one-piece metal castings. This is especially true with small propellers used with model racing boats. That is, the propeller blades and hub comprise a unitary piece of cast metal, with such metals as aluminum, stainless steel, berylium bronze, etc. being popularly employed. Cast propellers, however, are formed with one fixed set of design characteristics, such as blade pitch angle and number of blades, etc. Thus, if a given propeller does not optimally match a particular boat, the only way to change the propeller design characteristics is to bend or grind the blades. However, blade bending is inaccurate and tends to weaken the blades, and blade grinding is wholly irreversible. Unfortunately, the only other alternative is to purchase additional propellers until one with satisfactory design characteristics is found. As a practical matter, this is a lengthy and costly trial and error process. The propeller which is finally chosen is often only satisfactory, and does not achieve optimal boat performance.
It is therefore the object of this invention to provide apparatus and method for making a boat propeller from a hub and a plurality of blade blanks wherein the propeller has an individually chosen selected set of design characteristics. Further, it is the object of this invention to provide propeller making apparatus and method for making propellers of different sizes and shapes, and propellers which can be taken apart and reassembled as needed to meet different design criteria.